匹配分支中的逻辑“和”

Question

如何在match'手臂中表达逻辑'和'？

像下面这样：

fn main() {
    let expr: Result<_, ()> = Ok(String::from("hello"));
    let _res = match expr {
        Ok(s) && s.trim() != "" => s,
        _ => String::from("None"),
    };
}

Answer 1

使用matchguard：

fn main() {
    let expr: Result<_, ()> = Ok(String::from("hello"));
    let _res = match expr {
        Ok(s) if s.trim() != "" => s,
        _ => String::from("None"),
    };
}